The present invention relates generally to impact countermeasures for automotive vehicles, and more particularly, to hollow countermeasures structures used to reduce the force of impact on various portions of the interior of the automotive vehicle.
Resilient pads have been used to protect vehicle occupants from contact with the interior structure of the vehicle during an impact. One common way in which to prevent contact with the interior structure is to provide airbags. Airbags have been employed both in front and in side impact areas. However, airbags do not completely protect the vehicle occupant. Other areas of contact for the vehicle occupants may include the body pillars, roof structure, door header and the like. Commonly, expanded foam pads are employed in such areas. Expanded foam pads are formed of molded and expanded polypropylene or polystyrene foam. Using molded expanded polypropylene or polystyrene foam requires the use of long cycle time processes. Such materials are relatively expensive and the processes are expensive in that they are time consuming to form a part.
Another drawback to such devices is that as the design evolves for a particular automotive vehicle, the parts may have to be substantially reworked during the process.
It would therefore be desirable to provide a method for forming an impact countermeasure that is flexible to allow easy design changes as well as uses low cost materials and low processing times.
The present invention provides a countermeasure that uses a blow molding process to form a hollow part.
In one aspect of the invention, a countermeasure for receiving an impact force has a generally hollow device body that has an outer wall defining an interior portion and an exterior portion. The wall has at least one blow hole therethrough. The wall has at least one tack off area formed therein. The tack off area and the blow hole control the crush rate of the body in response to the impact force.
In a further aspect of the invention, a method for operating a countermeasure device comprises directing an impact force at a generally hollow device, counteracting the impact force by releasing air through a blow hole in a predetermined rate in response to the impact, and counteracting the impact by controllably crushing a tack off area.
In a further aspect of the invention, a method for making a countermeasure device comprises blow molding a device having a generally hollow device body having an outer wall defining an interior portion and an exterior portion, forming at least one blow hole through the outer wall, forming at least one tack off area in the outer wall, and achieving a crush rate by sizing the tack off area and said blow hole.
One advantage of the invention is that the blow molding process has a substantially reduced cycle time than the foam processes described in the background of the invention. Another advantage of the invention is that the device is easily tunable for different impacts by controlling the blow hole size. Thus, if the requirements of the vehicle are changed, the blow hole may be easily changed.
Another advantage of the invention is that the angles of the sidewalls of the tack off area may be easily changed or the shape may be changed to change the crushing characteristic of the device without having to change the entire device design.
Other advantages and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.